Horizontal drilling and hydraulic fracturing have improved hydrocarbon production from unconventional shale reservoirs and other tight reservoirs. To predict hydrocarbon production and to optimize production strategy from such reservoirs, understanding the hydrocarbon storage and transport mechanisms is beneficial. Low field NMR has proven to be a powerful logging technology for measuring fluid content and other properties in a geologic formation, for example, a hydrocarbon-bearing reservoir, and for characterizing fluid-solid interaction. It has also been used in the laboratory for accurate characterization of petroleum systems and for calibration of field log data.